Conversion Mechanism From Trivalent Bismuth to Bivalent Bismuth Defect Center in Bi-Doped Silica Optical Fiber

We present first-principle methods on the conversion of trivalent bismuth center in Bi-doped silica optical fiber. With the increase of Bi-O distance in different member rings, the reaction energy of transition state configurations gradually become larger. The reaction energy of Bi-6MR is greater than that of Bi-4MR, than that of Bi-5MR, respectively. Based on the basis of the time-dependent density functional theory (TDDFT), transition energy levels of bivalent bismuth defect center models are investigated. Our calculations reveal that the ~1310 nm luminescence of the second optical communication window is likely caused by bivalent bismuth defect center configuration.